1) Field of the Invention
The present invention relates to pulverulent, redispersible binders which are obtained by spray drying a dispersion comprising a water-soluble polymer, and also to their use in applications in the building industry, specifically for the modification of cement-containing compositions, the formulation of paint compositions and coating compositions.
2) Background Art
Pulverulent binders have a number of advantages compared to the corresponding aqueous formulations: they require a reduced transport and storage capacity and are less sensitive to the action of weathering, frost and microorganisms. To produce such pulverulent binders, spray drying is carried out using spraying auxiliaries which prevent caking or lump formation during the drying process and during subsequent storage and ensure easy redispersion in use.
The spraying auxiliaries known from the prior art have many disadvantages: use of the naphthalenesulfonic acid-formaldehyde or benzene-sulfonic acid-formaldehyde condensation products known from EP-A 78449 and EP-A 407889 gives colored products. The spraying auxiliaries known from DE-A 4118007 and EP-A 467103 impair the product properties of the polymers sprayed therewith when used as binders. EP-A 671435 describes water-soluble protective colloids which comprise olefinically unsaturated sulfonic acids or carboxylic acids, as spraying aids for acrylate dispersions.
It is an object of the invention to provide pulverulent, redispersible binders based on vinyl ester-ethylene copolymers which do not have the disadvantages in use of the known spraying auxiliaries.